Introducing mercury into discharge lamps



Oct. 2, 1956 s. F. SCHAEFER INTRODUCING MERCURY INTO DISCHARGE LAMPSFiled Feb. 27, 1953 H w M w Q 0 256262 z 5652 $5352 Ell/4 57+ 5757277 l5I9 'VOLUME m CuBn'c canrms rsrzs FROM CUMPRESSED A12 SYSTEM SYSTEM 1FROM EXHAUST THORIUM mums:

l nvsrsv WITH INVENTOR ZE'SKH/iEI-EE j 9 IATTORVNE United States PatentINTRODUCING MERCURY INTO DISCHARGE LAlVIPS George F. Schaefer, Ramsey,N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh,Pa., a corporatiou of Pennsylvania Application February 27, 1953, SerialNo. 339,226

1 Claim. (Cl. 53-12) This invention relates to the introduction ofmercury into discharge lamps and, more particularly, those of thehigh-intensity or high-pressure type having quartz envelopes.

The principal object of my invention, generally considered, is to avoidloss of part of the mercury to be introduced into the envelope of such alamp, after the same has been accurately measured and prior to itsactual reception in said envelope.

Another object of my invention is to introduce an accurate quantity ofmercury into a discharge lamp, said quantity depending on the size ofthe lamp and the distance between electrodes, by a method involving notonly facilitating the determination of the amount of mercury to beintroduced, but the prevention of any loss from that amount prior to itsintroduction.

A further object of my invention is the accomplishing of the resultabove mentioned by coating the surface of the mercury droplet ofmeasured quantity with a film of oxide of the group consisting of thoriaand zirconia, said method involving one of the following alternatives:

A. The dusting with a finely powdered refractory oxide of the interiorof the capsule used for introducing the droplet into the envelope.

B. Such dusting of the interior of the hollow arm or connecting tubeextending from the side of the discharge lamp envelope with such anoxide, prior to pouring the mercury droplet therethrough, and

C. The application of the oxide directly to the mercury droplet prior topouring the latter into the envelope of the discharge lamp.

Other objects and advantages of the invention will become apparent asthe description proceeds.

Referring to the drawing:

Figure 1 is an elevational view of apparatus employed for estimating thecapacity of the discharge lamp envelope into which mercury is to beintroduced.

Figure 2 is a graph showing how the requiredweight of mercury isdetermined from the volume of the envelope and the distance between theelectrodes, or length of the arc path.

Figure 3 is a diagrammatic view of apparatus for conveniently measuringthe desired weight of mercury.

Figure 4 is a fragmentary elevational view of the left hand end portionof said apparatus, showing how mercury after being measured isintroduced into a glass capsule.

Figure 5 is an axial sectional view of such a capsule, enlarged to showhow it is dusted with a refractory oxide.

Figure 6 is an elevational view of a discharge lamp such as shown inFig. 1, after the capsule has been introduced into anexhaust-preparation arm thereof, and at the time said arm is beingtipped-0E after exhaustion.

Figure 7 is a view corresponding to Fig. 6, but showing the lamp and itsexhaust arm at a subsequent position in which the arm and lamp have beeninverted to allow the mercury droplet to fall from the capsule to thelamp prior to tipping-off its exhaust-preparation arm.

Figure 8 is a transverse sectional view on the line VIII-VIII of Fig. 6,but to an enlarged scale.

Figure 9 is a view corresponding to Figure 8 but illustrating amodification.

Figure 10 is a view showing apparatus for practicing my invention, inaccordance with another embodiment.

The present method of introducing mercury into. discharge lamps, andspecifically quartz lamps of the highpressure type, involvesconsiderable difficulty at times to insure that the full amount, as thatin the glass tube or capsule customarily employed in the introduction,gets into the lamp. In humid weather, or in case the glassexhaust-preparation arm which projects from the lamp envelope is notabsolutely clean, the mercury droplet when introduced, as from thecapsule, into said arm, on its way to the lamp envelope, has a tendencyto separate into minute droplets or wetthe arm. The result is that insuch an instance the correct amount of mercury does not enter theenvelope of the lamp, resulting in many cases in low operating voltageso that the lamp must be scrapped.

My invention involves an improved method for correcting the aboveconditions. It essentially includes dusting or rolling the measuredamount of mercury for each lamp in finely pulverized thorium oxide,zirconium oxide, or other similar inert or stable metal oxide. I havefound that mercury when so dusted or superficially coated will rollfreely and, even if it separates into smaller parts, none of it will wetthe glass exhaust-preparation arm. Thus all of the measured quantity ofmercury will enter the lamp. My method also considerably reduces thetime required to get the mercury into the lamp.

Referring to the drawing in detail, like parts being designated by likereference characters, there is shown in Figure 1 as one embodiment, aquartz envelope 11 of a high-intensity mercury vapor lamp. Such a lampmay be of the type described and claimed in the Unglert et a1.application, Ser. No. 113,444, filed Aug. 31, 1949, now

Patent Number 2,675,496, and owned by the assignee of the presentapplication. As such it includes main electrodes 12 and 13 and anauxiliary electrode 14 sealed into the ends thereof. This figure alsoillustrates apparatus for determining the volume of the envelope 11, inorder to estimate the proper amount of mercury to be inserted thereinto.This amount depends, not only on the volume, but also on the arc lengthor distance between in a head 17, such as is conventionally used onexhaust machines, only diagrammatically illustrated. See the head 19 ofthe Campbell Patent No. 2,533,712, dated Dec. 12, 1950, the hand lever25 of which corresponds with the operating lever 20 of the present case.The head 17 is connected to an exhaust system through tubing 18, saidtubing having valves 19 and 21 therein and between which is connected'aglass bulb 22. The tubing 18 branches to a manometer 23 containing amercury column 24. Adjacent one arm of the manometer 23 1s-a scale 25,calibrated in cubic centimeters to show the volume of the envelope 11.

The arrangement disclosed is used by first exhaustingwith'the valve 19closed and the valve 21opened. The valve 21 is then closed and the valve19 opened. This employs the vacuum produced in the bulb 22 to draw someof the air from the envelope 11 and create a partial vacuum in thesystem, represented by a rise in the left hand column of mercury 24 tothe position illustrated, whereby the calibrated scale 25 shows thevolume of said envelope, in this instance 17 cc.

This reading, of 1-7 is employed by using the chart shown in Fig. 2 todetermine the required weight of mercury in milligrams. The arc lengthin millimeters enters the picture, as shown in this figure, as each lineof the graph is drawn in accordance with an arc length, that is, arelengths from 57 mm. to 63 mm. are shown. So the required weight ofmercury is determined by running from the point of intersection of theordinate marked 17', representing the volume, and the graph 57,representing the arc length, horizontally to the scale of "mercuryweight, where the reading. of 86 is found, meaning that 86 mg. ofmercury are required for such an envelope.

While this amount of mercury may be weighed out on a chemical balanceand used, as will be understood, yet my preferred method of measuring isto draw the mercury into a capillary tube 26, as shown in Figure 3, theWeight of the mercury being determined by its length in the capillaryfrom the inlet or left hand end, as shown by the scale 27'.

The mercury is drawn from a receptacle 28 containing a supply 29thereof, by means of a connection through a valve 31 to an exhaustsystem, as indicated. This drawing into the capillary to the properlength is controlled by carefully opening the valve 31, while the systemis otherwise closed by the operators finger 35 and the valve 3'8, todraw up the mercury column 32. If the column is' drawn up too far, itmay be released or allowed to fall back by closing the valve 31 andcarefully admitting some air to the rubber tube 33, connected to theextension 34 of the tube 26, by allowing leakage past the operatorsfinger 35.

When the desired amount has been measured, the receptacle 28 iswithdrawn, the capsule 36 (Fig. 4) into which" the mercury is to beplaced is positioned under the pointed end 37' of the tube 26, and themeasured quantity of mercury discharged thereinto by, with the valve3-]: and finger 35 closing the system, the latter serving to adjust thepressure, carefully opening the valve 38 from a compressed air system.

In accordance with my invention, the capsule 36 prior to receptionof'the mercury droplet 38, is coated on its interior, as by dusting,with an inert metal oxide, such as 'thoria, zirconia, or some otherrefractory oxide powder, either harmless or beneficial to the lampduring operation. This dusting may be effected by placing a quantity ofsuch capsules in a jar (not shown) pouring a quantity of thoria intosaid jar, and stirring, rolling or otherwise agitating the mass untilthe thoria, or other selected oxide, has worked into the interiors ofsaid capsules. The capsules are then removed, one by one, and their exteriorswiped oil, whereupon they are ready for the reception of mercurydroplets 38'.

Mercury from said capsules is introduced, preferably into an.exhaust-preparation arm 39 (Fig. 6) extending from an envelope 1]., asby being sealed to the tube 16 extendingztherefrom at a point indicatedat 41. This exhaust-preparation arm 39 comprises a quartz portion 42',sealed directly to the quartz tube 16, and a graded-seal portion 43,terminating in a glass portion 44, which may be of the type designatedby the trade-name Nonex, although any glass, which is readily scalableto the part 43 and thereafter tipped-off, may be employed.

The capsule 36 containing the droplet of mercury 38 is pushed up intothe tubular portion 44, to the position approximately illustrated inFig. 6, toward the envelope 11 asv the exhaust-preparation arm 39 isdepending therefrom. The capsule 36-may be held in this position bymeans of an inverted V-shaped spring 45 with its diverging ends engagingthe inner wall of the tube 44 and the capsule resting on the apex ofthis inverted V-shaped spring. The tube portion 44 is then inserted inan exhaust head 46, corresponding generally with the head 17, throughwhich the arm and connected tube 11 are exhausted in a conventionalmanner, as will be understoodi- After the tube 11 is exhausted to thedesired degree, the tube 44 is tipped-elf, as indicated at 47, as bymeansof apointed gas flame 4S issuing from a burner 49.

The envelope 1 audits connected exhaust preparation arm are theninverted to the position represented in Figure 7. This allows thecapsule 36 to drop by its weight from the apex of the V-shaped spring 45to the position illustrated, where it encounters a restricted portion 51in the tube 44 thereby stopping it from further movement while the nowreversed \l-shaped spring 45 remains fixed by itsv tension in the tube44, as shown in Fig. 7. The

mercury droplet, however, the surface of which has been coated withpowder from the inner surface of the capsule 36, passes directly throughthe portions 43 and 42 into the envelope 11, and is represented at 38.The tubular portion 42 is then tipped-off, as at 52 by the sharp flame53, and the lamp of the envelope 11 is then ready for use.

Figure 9 represents a modification in which the tubular portion 44 of anexhaust-preparation arm is coated interiorly with a finely powderedrefractory oxide, such as thorium oxide or zirconium oxide, as indicatedat 40, so that the mercury droplet being introduced becomes coated bycontact with said portion 44*. This is an alternative to the coating ofthe capsule 36 of Fig. 5, as indicated at 40". But it will be understoodthat, inasmuch as the exhaust-preparation arm may be used over and overagain, it will gradually become coated with such oxide if capsules 36are so coated and used therewith, so that' after such use it may notthen be necessary to coat such capsules 36.

Figure 10 represents another embodiment in which the mercury'droplet 38is coated or dusted with powdered thoria or zirconia 40*, by beingplaced in a glass disk 54, alongside a quantity of the selected oxide,and mov ing it around in' contact therewith until its surface is coatedwith said oxide. The droplet 38 may then be employed for insertion intoan envelope 11, as by dropping it directly into an exhaust-preparationtube thereof, or by placing it in a capsule 36 and employing it in themanner heretofore described.

Although preferred embodiments have been disclosed, it will beunderstood that modifications may be made within the spirit and scope ofthe invention.

I claim:

The method of introducing an accurate quantity of mercury into adischarge lamp comprising dusting the interior surface of a small glascapsule with a powdered oxide of. the group consisting of thoria andzirconia, measuring the desired quantity as a droplet of mercury,placing said droplet in said dusted capsule, introducing said capsuleinto a tubular arm attached to the envelope of said lamp, exhaustingsaid envelope through said arm, tipping off said arm beyond said capsulefrom said envelope, inverting to allow said mercury to flow from saidcapsule to said envelope, and tipping-oil said arm from said envelope.

References Cited in the file of this patent UNITED STATES PATENTS

